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Air changes in the pharmaceutical clean room play an important role in the maintenance of HVAC clean room quality. Air changes per hour are the number of total replacements of any room’s air in one hour.
If the supply of the air by HVAC system in one hour is equal to the volume of the room then it will be one air change per hour. Rooms having 60 air changes per hour will have 60 times air supply then the volume of the room. FDA recommends maintaining the minimum 20 air changes per hour in clean rooms.
How to Calculate the Air Changes Per Hour (ACPH Formula):
First of all, determine the velocity of the air below the HEPA filter in feet per minute. It is determined at the four corners and the center of the filter and the mean of the five readings are determined.
V = (V1+V2+V3+V4+V5)
5
V = Velocity observed at each point
Now calculate the area of the filter by multiplying the length and width of the filter in feet.
A = l x w
l = length of HEPA filter
w = width of HEPA filter
Calculate the total air volume per minute supplied in the clean room by the following formula:
T = A x V
A = Area of HEPA filter in square feet
V = Average air velocity in feet per minute
Calculate the total air in the room multiplying the length, width and height of the room in feet.
Volume = L x W x H
Now we can calculate the Air Changes per hour using the following formula:
Air Changes per Hour = T X 60
Volume
Related: Cleanroom Validation
The requirement of number of air changes per hour for any room depends on the class of the room, number of personnel working in the area and frequency of access the room. Cleanliness of any clean room is maintained by the air changes per hour. More air changes per hour are required for the better clean room class than the lower one.
More air changes per hour are required to maintain the area where dust is generated as in granulation and tablet compression areas. In these areas dust is to be removed in a short period, hence more air changes per hour are required.
Following is the list of the air changes per hour in different classes of classified area.
Cleanroom Class

ISO Class

Required Air Change per Hour

100

ISO 5

240480

1,000

ISO 6

150240

10,000

ISO 7

6090

100,000

ISO 8

548

Therefore the air changes per hour show the quality of the air in the cleanroom that helps the maintenance of the clean area quality.
Air changes are not a requirement, they are a recommendation and are based on a rule of thumb. Air change rate alone is no guarantee for an effective airflow in a clean room  depends on situation of supply and extract grids, number and activity of personnel,....
ReplyDeleteAir changes are not a requirement, they are a recommendation and are based on a rule of thumb. Air change rate alone is no guarantee for an effective airflow in a clean room  depends on situation of supply and extract grids, number and activity of personnel,....
ReplyDeleteCAN U PLEASE TELL ME HOW TO CALCULATE THE CFM REQUIRED FOR A ROOM
ReplyDeletevol of room multiply by air change per houre divided by 60
DeleteCFM= Volume of room x ACH / 60
ReplyDeleteNote: ACH means air changes in one hour
hi
ReplyDeleteCan ACPH be calculated based on return Air(Exhaust air) in vegetative room. . specially for Pharmaceutical clean room.
my results is wrong . please hepl me
ReplyDeletesize of duct 8.1 x 5.3 x 5.7
velocity 0.4
vloume of room 7564.5cubic feet
please sort out my problem
How many filters in HVAC System & which Microns?
ReplyDelete3type filter use in HVAC system
ReplyDelete1pre filter 10 micron
2fine/micro filter 5 micron
3hepa filter.3 micron